1. Field of the Invention
The present invention relates to a hydraulic braking pressure control device incorporated in a braking system for a vehicle in which two independent hydraulic lines are extended from a dual type master cylinder to front and rear wheel brakes, and more particularly relates to a hydraulic braking pressure control device which is constructed such that the rear wheel brakes are supplied with a hydraulic pressure lower than that for the front wheel brakes.
2. Description of the Prior Art
A conventional type of braking system for a vehicle is typically illustrated in FIG. 1 in which pairs of diagonally located front and rear wheel brakes B.sub.f, B.sub.r ' and B.sub.f ', B.sub.r are connected to one another by way of the mutually independent first and second hydraulic lines L.sub.1 and L.sub.2 both of which extend from the delivery ports of the master cylinder M. Further, another conventional type of braking system is constructed such that the front wheel brakes B.sub.f and B.sub.f ' are each provided with two hydraulic braking mechanisms which are connected with the first and second hydraulic lines L.sub.1 and L.sub.2, respectively. With this braking system, in order to ensure that effective braking is effected by automatically reducing hydraulic pressure for the rear wheel brakes at a certain ratio relative to that for the front wheel brakes when rear wheel load is decreased due to forward inclination of the vehicle body during powerful braking operation, there is provided a hydraulic braking pressure control device V which is disposed commonly in the first and second hydraulic lines L.sub.1 and L.sub.2 extending from the master cylinder M to the rear wheel brakes B.sub.r and B.sub.r '.
It has been hitherto pointed out with the conventional braking system that this type of control device V has to be provided with a by-pass function in order that the intended powerful braking is attained for both the front and rear wheels merely by one of two hydraulic lines when the other one fails to be properly operated.